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I hadn't really planned to make a thread for this, but the result has been pretty satisfying so I figured I'd share the the progress pics with you guys. The idea was to delete some of the deep bass/droning noise of the M50, and change it to a more pitchy sound, hopefully giving it some more character that I'd always loved about my previous Red E30 with the M20. I'd researched, listened to, and noted down different setups, from generic Ebay headers, Hiop headers, Racelands, etc. After sifting through countless header designs, I settled on two different ones that would have assured me to get rid of that 'truck sound' that the M5x makes. The first were a set of gorgeous Euro S50 headers, and the second was the custom and hard to find World Challenge E46 spec 6-2-1 headers from Kromerkraft. Well... needless to say, S50 are a dime a dozen compared to KK headers, so I purchased a set of those awhile back. And they didn't fit. At all. Hitting firewall, sway bar, sticking down too low, etc... and I couldn't bring myself to cut them up because they are a work of art. So I pondered on it for awhile and let the idea simmer.

Great to put on a wall or something, but kind of useless for me now!

When I finished my recent M42 swap into my 2002, I thought back to the part of the headers where I had to cut the original, and manipulate the collector so it fit better in the car. I was pretty happy with the outcome of that slight modification and thought, hey, why not cut up some 318 headers and make a set of 6cyl headers?! The wheels were turning! At first, a few of my friends thought I was dumb to even think to attempt such a project. I ended up using a total of three 318 header setups for this as well as a set of Genie shorty headers for the collectors and a few of the bends towards the end when I ran out of 318 pipes to use.

Genie Headers. Not the nicest things in the world, but they served their purpose well for me.

Thanks to 325isStephen and oldschool on this board for hooking up 318 manifolds for the project!

Initially, I only had 2 318 manifolds to work with, thinking those, plus the Genies would have been enough. Boy, was I wrong! But, I'll get to that in a second. When I had the first 318 manifold in-hand, I stared at it for awhile thinking which pipes would route the best for the header, so I mocked it up on a cylinder head to see. Haha, hey look, #2 of the M42 upsidedown makes a perfect #6!!

I cut apart each runner at the flange (M44 being the friendliest one to cut) and started to mockup which pipe went where

I figured, lets start with the hardest ones first, make sure they will even fit the car, and then press on. I knew there was no way the original version of this header style would even fit in an E30, so I basically had to make a condensed version to fit without hitting anywhere. Making #5 and 6... hey it fits!

Holy crap, I'm getting somewhere! At this point, I found the project fun.

Pressing on, getting all the cylinders mapped out. This is the point where I figured it was time to cut up the Genies for the collector since I felt things were progressing well. It was also this point where I realized that I needed one more 318 manifold as I was running out of pipe and still had a bit more to go.

Then to finish a runner, tack it on, and go see if it still fits the car!

So it fits! Finish it with the collector!

And all together!

At this point, I started with the install, and got rather frustrated. I guess my M50 parts car had different engine mounts, as that was the only thing different, because on my M52, the headers did not fit. It was touching the strut tower, brushing the sway bar, etc. Long story short, it ended up fitting, but the strut tower needed a slight bit of massaging to fit the #5 runner... and I also had to recut the collector on the 4-5-6 header as it was almost pointing at the ground in relation to pointing out towards the back. That was my fault for copying the original design made for an E46 which has a lot more room for the downpipe section.

This is the only pic I have of everything installed.

In total, it took me about 4 days to make the header. Would I do it again? Hmm... tough call but I'd say yes, BUT only when I know how to tig weld. It would have turned out much cleaner, as mig for this is not ideal IMO. I also would have to liked to have used proper piping, bends, and nice flanges... as essentially I was working with 'junkyard' parts. All in all, I think it was a great first attempt for a header... and only better results will come from the next one!

So you must be wondering about the sound Lets say its a cross between a VR6, and a VQ35. I definitely have never heard an M5x sound like this before. I haven't gotten a chance to grab a sound clip of it yet, but come see it in person at Bimmercruise this weekend!

Still don't have an outside sound clip... but I have an interior view from this past weekend from the autoX at Bimmercruise! It sounds a bit different than the last time I had the same camera in the car back in April, but it doesn't do it justice as it sounds much better in real life. I still need to sort out the rear part of the exhaust to ditch some of the rasp.